Technique to examine an object

ABSTRACT

The invention relates to a process to examine at least one object, whereby properties of the object are detected at different times within a spatial-frequency space formed by spacial-frequencies.  
     According to the invention, the process is carried out in such a way that consecutive images are recorded in overlapping areas of the spatial-frequency space and, additionally, in areas of the spatial-frequency space that differ from each other.

DESCRIPTION

[0001] The invention relates to a process to examine at least one object, whereby properties of the object are detected by various measurements within a spatial-frequency space formed by spatial frequencies.

[0002] Preferably, the various measurements take place at different times.

[0003] Examinations of the spatial-frequency space are employed in a wide array of technical fields. Since pulse spaces correspond to spatial-frequency spaces, the term spatial-frequency space also encompasses pulse spaces. The designation spatial-frequency space serves to clarify the fact that the invention also relates to a process in which no pulse transmission occurs.

[0004] A known problem encountered when imaging spatial-frequency spaces is that a very long measuring time is needed when a high local resolution is combined with a high spatial-frequency resolution.

[0005] A keyhole process for solving this problem is known. In this process, a high-resolution image involving the detection of the entire spatial-frequency space is determined at least at one point in time. In one or more measuring steps, a central area of the spatial-frequency space is imaged that determines the contrast of the reconstructed image. Subsequently, the high-resolution image is mathematically linked to the recorded image(s) of the central areas of the spatial-frequency space in such a way that a high-resolution image having a contrast that corresponds to the point in time of the recording is determined for the other time or times.

[0006] This known process has the disadvantage that contrast changes between consecutive measurements can only be determined if they have a sufficiently large spatial extension.

[0007] This disadvantage is particularly detrimental when functional parameters are being detected

[0008] Thus, for instance, in functional magnetic resonance imaging, there is a need for parameters that influence nuclear magnetic resonance signals to be detected with the highest possible spatial resolution.

[0009] The invention is based on the objective of creating a process with which it is possible to detect a change in parameters when the spatial areas affected by the change are relatively small.

[0010] This objective is achieved according to the invention in that various measurements take place in at least one shared area of the spatial-frequency space and, additionally, in areas of the spatial-frequency space that are different from each other.

[0011] Preferably, the measurements detect the spatial-frequency space in images taken at different times.

[0012] In particular, the invention provides for examining areas of the spatial-frequency space at rates of occurrence that differ from each other, whereby preferably there are at least three different rates of occurrence for detecting areas.

[0013] It is advantageous for the measurements of the areas to take place with at least three different detection rates of occurrence.

[0014] Preferably, at least one, for instance, centrally located area of the spatial-frequency space is detected in several measurements while other areas are not detected at all or else only detected in a single measuring procedure.

[0015] It is advantageous to carry out the process in such a way that the overlapping areas cover a central region of the spatial-frequency space.

[0016] An advantageous embodiment of the process is characterized in that the additional, preferably not central, areas in the spatial-frequency space are at a distance from each other that is greater than their spatial-frequent extension in the direction of this distance.

[0017] It is advantageous to carry out the process in such a way that the other areas of the spatial-frequency space extend, at least partially, parallel to each other.

[0018] Here, it is especially advantageous for the disjunctive elements of the individual sets to extend, at least partially, parallel to each other in the spatial-frequency space.

[0019] An advantageous embodiment of the process is characterized in that the measurements are carried out in such a way that a cycle is formed in which at least some of the areas of the spatial-frequency space that differ from each other are once again detected in additional measurements.

[0020] An advantageous embodiment to carry out the process is characterized in that the areas detected form a disjunctive set in at least one measurement.

[0021] Additional advantages, special features and practical improvements of the invention ensue from the subordinate claims and from the following presentation of a preferred embodiment of the invention with reference to the drawing.

[0022] The drawing shows a schematic depiction of a detection of a spatial-frequency space with several consecutive measurements.

[0023] The image shows the detection of a spatial-frequency space with N x N points as an example.

[0024] For purposes of simplifying the graphic representation, a two-dimensional depiction was chosen, although the invention is by no means restricted to the detection of two-dimensional spatial-frequency spaces, but rather, it is suitable to detect spatial-frequency spaces having any desired number of dimensions.

[0025] A first measuring procedure detects a central area 1 as well as areas 10 of the spatial-frequency space that are at a distance from the central area 1—represented here in the form of broken lines—and that are preferably essentially parallel to the spatial-frequency space.

[0026] In a subsequent measuring procedure, the central area is detected once again. In addition, other areas 20—represented by the dash-dot lines—of the spatial-frequency space that lie outside of the central area 1 are also detected. The other areas 20 of the spatial-frequency space preferably extend parallel to each other and anti-parallel to the other areas 10 detected in the preceding measuring step.

[0027] Subsequently, the measuring procedure is repeated. In this repetition, the central area 1 as well as other areas 30—indicated by the dash-dot-dot lines—of the spatial-frequency space are detected.

[0028] By means of a merely selective detection of the high-frequency data, the time advantage of a keyhole method is essentially maintained. Moreover, noise effects are suppressed.

[0029] Furthermore, the images shown have a high spatial resolution corresponding to the overall images of the spatial-frequency space.

[0030] It is particularly advantageous to image a suitable SPARCE sequence.

[0031] Preferably, an imaging pattern corresponds to a SPARCE sequence having the following formula:

SPARCE(f,n)=[N/2−n, N/2−f−n, N/2−2f−n, . . . (KEYHOLE) . . . −N/2+3f−n, −N/2+2f−n, −N/2+f−n]

[0032] In an advantageous manner, the entire spatial-frequency space is imaged, whereby the spatial-frequency space can be considered, for example, to be an N×N image matrix. The image matrix has a slight covering of high spatial frequencies as well as a more thoroughly covered, so-called keyhole area.

[0033] A SPARCE sequence, SPARCE <fn>, contains indices f,n, wherein f stands for an image factor and n for a running time variable, whereby it applies that (0≦n<f).

[0034] By means of a relatively small or infrequent detection of areas having high spatial frequencies, a time advantage is achieved, in addition to which the correlation between high-frequency noises is reduced, which is something particularly advantageous.

[0035] Another improvement can be achieved with an even-numbered sampling factor f in that even and odd echoes are detected separately.

LIST OF REFERENCE NUMERALS

[0036]1 central area

[0037]10 additional areas of the spatial-frequency space

[0038]20 additional areas of the spatial-frequency space

[0039]30 additional areas of the spatial-frequency space 

1. Process to examine at least one object, whereby properties of the object are detected by various measurements within a spatial-frequency space formed by spatial frequencies, characterized in that various measurements are taken in overlapping areas of the spatial-frequency space and, additionally, in areas of the spatial-frequency space that differ from each other.
 2. Process according to claim 1 , characterized in that measurements of the areas take place with at least three different detection rates of occurrence.
 3. Process according to one or both of claims 1 and 2, characterized in that the areas that overlap cover a central region of the spatial-frequency space.
 4. Process according to one or more of the preceding claims, characterized in that the additional areas in the spatial-frequency space are at a distance from each other that is greater than their spatial-frequent extension in the direction of this distance.
 5. Process according to one or more of the preceding claims, characterized in that the additional areas of spatial-frequency space extend, at least partially, parallel to each other.
 6. Process according to one or more of the preceding claims, characterized in that elements of the detected areas form a disjunctive set in at least one measurement.
 7. Process according to claim 6 , characterized in that disjunctive elements extend, at least partially, parallel to each other in the spatial-frequency space.
 8. Process according to one or more of the preceding claims, characterized in that the measurements are carried out in such a way that a cycle is formed in which at least some of the areas of the spatial-frequency space that differ from each other are once again detected in additional measurements. 